Telephone system.



Patented May 14, 1912.

- WITNESSES:

coLunllA PUNOGKAPK :0" WASHINGTON. n. c.

FREDERICK R. PARKER, OF CHICAGO, ILLINOIS.

TELEPHONE SYSTEM.

Application filed November 23, 1904, Serial No. 234,089.

Specification of Letters Patent.

Patented May 14, 1912. Renewed August 23, 1911. Serial No, 645,630.

To all whom it may concern:

Be it known that I, FREDERICK It. PARKER, a citizen of the United States of America, residing at Chicago, in the county of Cook and State of Illinois, have invented a new and useful Telephone System, of which the following is a specification, reference being had to the accoi'npanying drawings, illustrating same.

My invention relates to electrical transmitting systems and in particular to telephone systems.

The principal objects of my invention are to provide improved means for operating and controlling the subscribers or line-signal indicators or annunciators in such a system; to provide improved means for operating and controlling the supervisory or disconnect indicators or annunciators in such a system; to provide improved arrangements of the parts, devices and circuit connections, in such a system; and to provide a telephone system which may be eliiciently and effectively operated and utilized without the employment of relays.

Other objects will be apparent from the following specification.

In telephone systems, especially of the central energy or common battery type, it is generally the practice to employ relays to control the circuits of the signaling devices of the system, that is, the line signaling devices and supervisory signaling devices. In my present invention I preferably do away with all of these relays and arrange the circuits of the system so that the line signaling devices and supervisory signaling devices are directly shunted to render them inoperative, when it is desired to extinguish their signals to keep them from displaying signals. I preferably shunt the line signaling device of a line by a resistance or impedance associated with the plug-cord circuit, when connection is made with this line, and preferably shunt the supervisory signaling device which is now connected with the line, by the circuit of the line when same is closed. I preferably en'iploy high resistance line and supervisory signaling devices, or high-resistances in series therewith, to make the shunt circuits more effective; and it is upon the proper proportioning of all of the resistances of the system that its successful operation depends.

I will more particularly describe my in- .Vention by reference to the accompanying drawings illustrating suitable means for accomplishing the desired results, in which,

Figure l is a diagram showing two subscribers lilies and the central station signaling and connecting apparatus; and Fig. 2 is a diagram of a cord circuit showing the windings of a repeating coil in series with the respective supervisory signals and the main strands of the respective connecting cords.

Like characters refer throughout the drawings.

The line of subscriber A extends in two limbs a and 7) from a substation to a central station. Limb (t is connected to connection terminals 0 c of the several spring jacks D D of the multiple switchboard, and through conductor 0, and winding ft of impedance coil I, to pole on of battery (I; and limb is connected to terminals cl (Z of the several spring jacks D D, and through c011- ductor f, line-signal lamp and winding 1' of impedance coil I, to pole or of battery Q.

At the subscribefis station A, the line conductors u and b are preferably normally discminecled from each other, but are adapt ed to be conductively connected together through the subscribefs telephone when the receiver is taken from the switcli-hook, in a manner well understood.

The line of subscriber B is similar to that of subscriber A, except that in line B I preferably show lamp 9 connected direct to pole a of battery Q, through conductor hen lamp g is connected direct from a limb of the line to the central source of electricity, as in line B, it is preferably of a high resistance.

In the plug-cord connecting circuit, tip strand a, of answering plug I is normally connected through condenser (1,, contact n. and spring m, of ringing key H, to tip strand "u, of calling plug l Sleeve strand 1)., of answering plug I is normally connected through condenser f spring 7)., of listening key G, contact 0,, contact 9 and spring 8,. of ringing key H, to sleeve strand 7), of calling plug F. Spring j, of listening key G is connected with contact a, and condenser e Supervisorysignal lamp 0, is connected from tip strand c of answering plug I preferably through winding (Z of impedance coil N, to sleeve strand 2), of said plug E. Supervisory lamp is connected from spring 7), to contact is which normally engages spring j Sleeve strand 1), of anto like parts swering plug E is connected through impedance coil 0 and conductor g to pole at of battery Q, and spring 79-, is connected through conductor 10,, impedance coil P, and conductors a, and j, to pole u of battery Q. It is immaterial which is the positive or negative pole of battery Q. The operators telephone is to be connected from contact 2', to contact 9 in a manner well understood. A ringing generator is to be connected from contact Z to contact 16 also in a manner well understood.

When the listening key G is depressed, springs j, and p, are disengaged from contacts k and 0 respectively, and engaged with contacts 2', and 9,, respectively. hen the ringing key H is depressed, springs m, and s, are disengaged from contacts a, and 1",, respectively, and engaged with contacts Z and t respectively.

The operation of the system is as follows: If subscriber A desires to talk with subscriber B, he lifts his telephone receiver from the switch-hook, in the usual manner, and thereby closes the circuit of battery Q through winding h of impedance coil 1, conductor e, limb a. of the telephone line, substation A, limb b of the line, conductor f, lamp and winding 2' of impedance coil 1, which causes lamp 9 to light and thereby convey to the operator the signal for connection. The operator thereupon inserts answering plug E into a spring jack D, or any suitable connecting means, of line A, which closes the circuit of battery Q through winding h of impedance coil I, conductor 6, jack spring 0, tip strand a supervisory lamp 0,, winding d of impedance coil N, sleeve strand 1),, jack spring d, conductor f, lamp g, and winding z' of impedance coil I; and through winding 7;, of impedance coil 1, conductor 6, jack spring 0, tip strand 01, lamp 0,, impedance coil N, impedance coil 0, and conductor 1 It will now be observed that the-path including jack spring a, tip strand 0,, lamp 0,, impedance coil N, sleeve strand 2),, and jack spring (Z, is shunted by the path including limb a of the telephone line, substation A, and limb b of the line; and that the path including conductor 7, line lamp 9,

' and winding 2' of impedance coil 1, is shunted by the path including winding h, of impedance coil 0, and conductor 1 In other words, the supervisory signal 0 and impedance coil N are shunted by the line and substation apparatus belonging to subscriber A, and the line signal 9 and winding 2' of impedance coil I are shunted by impedance coil 0. The resistance of the supervisory signal 0 and impedance coil N, is high, as compared with the resistance of the line and substation apparatus of subscriber A, and therefore the supervisory signaling device 0 now gets insufiicient current to cause it to display a signal, as the line of subscriber A takes the greater part of the current flowing over the combined paths of the line and the supervisory signal, as described, thus shunting the supervisory signal 0 out. The resistance of the line signal 9 and winding 2' of impedance coil I, belonging to line A, is high, as compared with the resistance of impedance coil O, and therefore the line signaling device 9 now gets insuflicient current to cause it to display a signal, as the impedance coil 0 takes the greater part of the current flowing over the combined paths of the line signal and impedance O, as described, thus shunting the line signal 9 out. The operator then depresses her listening key Gr, thereby causing .springs j, and p, to disengage contacts and 0 respectively, and engage contacts 1', and Q2, respectively, which bridges her telephone set across the plug-cord talking circuit in a manner well understood.

After learning that subscriber B is the subscriber called for, and after testing the line B in any suitable manner and finding same to be not in use, the operator then inserts the calling plug F into a spring jack D of line B and then depresses the ringing key H, thereby causing springs m, and s, to disengage contacts a, and 9",, respectively, and to engage contacts Z, and t respec tively, which signals subscriber B in a manner well understood. (In depressing the ringing key H, the operator also restores the listening key G to its normal position.) lVhen subscriber B responds and lifts his telephone receiver from the switch-hook, the subscribers A and B are connected for conversation with each other.

During the operation of calling subscriber B, a small amount of the calling current may pass through conductor 6, impedance coil K, battery Q, conductor j, lamp g, and conductor f, but as the impedance of winding h of impedance coil K, and the resistance of lamp 9, are preferably high, this current will beinappreciable. When line B is thus connected for conversation over same, the path including jack spring 0, tip strand 20 spring 7%,, contact 0%,, spring j,, contact 70 supervisory lamp 9,, spring 79,, contact 0,, contact 7-,, spring 8 sleeve strand 1),,

and jack spring cl, is shunted by the path the line signal 9 of line B is shunted by the impedance coil P. The resistance of the supervisory signaling device 9, is high, as compared with the resistance of the line and substation apparatus of subscriber B,

and therefore it now gets insufficient current from battery Q to cause it to display a signal, as the line B takes the greater part of the current flowing over the combined paths of the line and the supervisory signal, as described, thus shunting the supervisory signal out. This supervisory lamp 9, preterably has a very high resistance, say from 750 ohms to 1200 ohms, and requires a very small current, say from .05 of an ampere to .04 of an ampere, to light it to candle power. The resistance of the line signaling device 9 of line B, is high, as compared with the resistance of impedance coil 1, and therefore it now gets insufficient current from battery Q to cause it to display a signal, as the impedance coil P takes the greater part of the current flowing over the combined paths of the line signal and impedance coil P, as described, thus shunting the line signal out.

When the conversation is completed and subscriber A hangs his telephone receiver upon the switch-hook, he breaks the circuit over his telephone line in a manner well understood, and thereby takes the shunt away from the supervisory lamp 0 and allows it to light, thus conveying to the operator the signal for disconnection. The supervisory lamp 0 new lights over the path including winding 71. of impedance coil I,

conductor 6, jack spring 0, tip strand (4,,

lamp 0,, impedance coil N, impedance coil 0, and conductor 7 The path including sleeve strand 7),, jack spring (Z, conductor f, lamp g, and winding 2' of impedance coil I, is now shunted by impedance coil 0 and conductor g and hence the line signal 9 remains extinguished.

WVhen subscriber B hangs his receiver upon its switch-hook, he preferably breaks the circuit over his telephone line and thereby takes the shunt away from the supervisory lamp 9, and allows it to light, thus conveying to the operator his signal for dis connection. The supervisory lamp g now lights over the path including winding it of impedance coil K, conductor 6, jack spring a, tip strand 1a,, spring m contact vi spring j contact lamp conductor 10,, impedance coil P, and conductors e and The path including spring 7),, contact 0 cont-act r spring 8 sleeve strand 0),, jack contact cl of line B, conductor 7, and line signal lamp 9, is now shunted by conductor 10,, impedance coil P, and conductor 2,, and hence the line signal g belonging to line B remains extinguished.

It is evident that if either subscriber A or B should again remove his telephone receiver from the switch-hook while connection is still made with his line, he would cause his supervisory signal to be extinguished. Therefore by operating his switchhook, (alternately closing and opening the circuit of the line) either subscriber may signal the operator for a second connection, while connection is still made with his line, through the agency of his supervisory signal.

\Vhen the operator receives both disconnect signals from subscriber A and B, respectively, she withdraws the connecting plugs E and F from their respective spring jacks, thereby breaking the circuits of battery Q, from the supervisory signals 0., and {/2 and restoring both lines and all circuits and apparatus to their normal condition.

It is evident that subscriber B may be the calling subscriber and subscriber A the called subscriber, in which :ase answering plug E would be connected with line B, and calling plug F with line A, and the ope z tious with lines A and B being interchanged.

For the supervisory signal lamps I preterably use lamps requiring a small current to light them, say from .05 of an ampere to .O l of an ampere, and consequently of a high resistance in relation to their voltage.

The doublewound impedance coil I which I preferably use in line A, is a distinct improvement over two separate impedance coils, in that the windings of the double-wound coil exert a mutual induction on each other, in addition to the self-inductions of the single-wound coils, the said mutual induction tending to greatly reduce the flow of alternating currents from one limb of the telephone line through the central source of electricity and the windings ot' the double-wound coil I back to the other limb of the line, and hence resisting the flow of talking currents through the said windings. The double-wound coil gives the mutual induction and self-induction whereas the single-wound coils give only the self-induction.

In Fig. 2, I have shown the supervisory signals (1 and {/3 connected in circuit with respective windings (Z and of a repeating coil L, signal 0,, and winding cl, being also connected in circuit with tip strand a, and sleeve strand 1), of answering plug E,.and signal 9,, and winding ,1, being normally connected through listening key G and ringing key II, in circuit with tip strand u, and sleeve strand a, of calling plug F. \Vith this arrangement the condensers c and f 01 Fig. 1 are done away with and the central source of current is preferably connected to one strand of each connecting cord through conductor 7' and a single impedance coil M, preferably as shown. The supervisory signals 0,, and g, operate similarly to supervisory signals (1 and of Fig. 1. The talking currents traverse the supervisory signals 0,, and being repeated from one telephone line to the other through the repeating coil L, in a manner Well understood. The talking currents traversing line A, answering cord E, supervisory lamp 0, and winding 6Z3 of repeating coil L, are repeated through winding f, of repeating coil L, supervisory lamp 9,, calling cord F and line B, or vice versa, if connection is made with lines A and B. In depressing the listening key the operator preferably connects her telephone set in circuit with contact 2' spring 7' condenser 6 lamp 9,, winding f of repeating coil L, spring 29 and contact Q2, springs 7' and p, at the same time disengaging contacts 76 and 0,, respec tively. Nhen the key G is thus depressed, the talking currents from the operators telephone are repeated through the repeating coil L to the line which is connected with answering plug E, or vice versa.

In speaking of signaling devices, or the like, I contemplate any suit-able electricallyoperable device, as, for example, an annunciator having a visual signal.

It is also intended that a relay cont-rolling a signal shall come within the scope of the appended claims.

While I have illustrated my invention in connection with particular types of spring jacks, connecting plugs, listening key, ringing key, lamps, repeating coil, impedance coils, subscribers instrument, source of electric current, etc., it is to be understood that different types of these several pieces of apparatus may be used in this invention with good results.

l/Vhile this invention is illustrated in connection with multiple switchboard systems, it will be understood that its features are also applicable to telephone systems of the single, transfer, or divided-board types.

I do. not wish to limit this invention to all of the particular details herein set forth, as various modifications thereof may be made or utilized without departing from the scope of the appended claims.

Having thus described my invention, what I claim as new is 1. The combination with a telephone line and connection terminals therefor, of a signaling device associated with the line, a plug-cord circuit adapted to be connected with the connection terminals, a source of electricity associated with the line, a resistance through which the said source is associated with a main strand of the cord circuit, a lamp in series with a resistance, bridged across the main strands of the cord circuit, and means whereby, when connection is made with the line, the circuit of the said source is closed through a main connection terminal of the line, a main contact of the connecting plug, a main strand of the con necting cord, the said lamp with its resistance, and the resistance through which the said source is associated with the cord circuit, thus lighting the said lamp, substantially as described.

2. A telephone line having a connection terminal, a central source of electricity associated with the line, connecting means for the line comprising a pair of conductors to be included in the talking circuit, signalinitiating means in a series circuit with a portion of the said pair of conductors,means whereby the said signal-initiating means is supplied with electricity from the said source from the telephone line through the connection terminal, for actuating the signal-initiating means, when connection is made with the line, and means whereby the telephone line shunts the signal-initiating means, relatively to the said source, when connection is made with the line and the latter is in use, to render the said signal-initiating means inactive.

3. A telephone system having a plurality of lines extending to a central station and supplied by a common source of electricity,

in combination with a connecting circuit for the lines having a pair of conductors to be included in the talking circuit, a condenser in each conductor of the pair, a signal-initiating device connected across the said pair of conductors on one side of the said condensers, means whereby the signalinitiating device is supplied with electricity from a telephone line through a portion of one of the said pair of conductors when connection is made with the line, and means whereby the telephone line shunts the signal-initiating device to render same inactive when connection is made with the line and the latter is in use.

4. A telephone line extending from a substation to a source of electricity at a central station, a connecting circuit for the line, a lamp bridged across the talking strands of the connecting circuit, means-whereby connection with the line supplies the said lamp with current to light same, over a portion of the line extending to the said source, when the line is not in use, the said connection causing the line extending to the substation to shunt the said lamp out when the line is in use.

5. An electrical transmitting line, a connecting circuit therefor having conductors for transmitting the electrical transmission currents of the line to another line, a signal-initiating device bridged across the said conductors, and a central source of electricity having connections exterior of the said bridge for supplying the said device with energizing current, at least one of the said connections being through a line connection when connection is made with the line.

7. A telephone line, a connecting circuit therefor having conductors adapted to be included in the talking circuit, a signal lamp bridged across the said conductors, a source of electricity exterior of the said lamp bridge, and means whereby the said lamp is supplied with electricity from the said source over a line connection, for lighting the said lamp, when connection is made with the line.

8. A telephone line, a connecting circuit therefor having a conductive path comprising portions of the main strands of the corn necting circuit and a signal-lamp, a source of electricity exterior of the said conductive path, and means whereby the said lamp is supplied with electricity from the said source over a line connection, for lighting the said lamp, when connection is made with the line.

S). An electrical transmitting line, a connecting circuit theretor having conductors for transmitting the electrical transmission currents of the line to another line, a signalinitiating-deviee-bridge across the said conductors. a central source of electricity for supplying current through the said bridge to energize the said device, and suitable circuit connections whereby the said line when in use forms a shunt-circuit around the said bridge to render the said device inactive, the said shunt-circuit including no part of the said bridge.

10. The combination with a telephone line of a connecting circuit therefor having a pair of talking strands, a signal-initiatingdevice-bridge across the said talking strands, a central source of electricity for supplying current through the said bridge to actuate the said device, and suitable circuit connections whereby the said line when in use forms a shunt-circuit around the said bridge, in relation to the said source, to render the said device inactive, the said shunt-circuit including no part of the said bridge.

11. The combination with a telephone line and a connecting circuit therefor having a pair of talking strands, of an inmedancebridge across the said talking strands, said bridge containing a signal-initiating device, a central source of electricity for supplying current through the said bridge to actuate the said device, and suitable circuit connections whereby the said line when in use terms a shunt-circuit around the said bridge, in relation to the said source, to render the said device inactive, the said shunt circuit including no part of the said bridge.

12. A telephone line, a connecting circuit therefor having conductors adapted to be included in the talking circuit, a signallamp bridge across the said conductors, a source of current for lighting the said lamp, and suitable circuit connections whereby the said line when in use forms a shunt-circuit around the said lamp bridge to render the said lamp inactive, the said shunt-circuit including no part of the said bridge.

13. A telephone line, a connecting circuit theret'er having talking limbs adapted to be connected with the line, a signal lamp constructed to carry a maximum current not greater than approximately five-onehundredths of an ampere and bridged across the said talking limbs, a source of current having connections exterior of said bridge for lighting the said lamp, and suitable circuit connections whereby the said line when in use forms a shunt-circuit around the said lamp to render same incapable of displaying a signal, the said lamp permitting a line of exceptionally high resistance to shunt it as specified.

14. In a telephone system having lines extending to a central station, a metallic connecting circuit for the lines terminating in a pair of connecting devices, a condenser in each limb of the metallic connecting circuit, a signal-initiating device bridged across the said metallic connecting circuit, and a central source of electricity having connections exterior of the said bridge for supplying the said device with energizing current. at least one of the said connections being through a line connection when connection is made with a line.

15. In a telephone system having lines extending to a central station, a metallic connecting circuit for the lines terminating in a pair of connecting devices, a condenser in each limb of the metallic connecting circuit, a signal-initiating-device bridge across the said metallic connecting circuit, means for energizing the said signal-initiating device as dcsircd. and suitable circuit connections whereby the said signal-initiating device is shunted and thereby rendered inactive, by a line circuit when connection is made with a line, the said line-circuit shunt forming no part of the said bridge.

16. A telephone line, a connecting circuit for the line having a pair of conductors to be included in the talking circuit, a signalinitiating device bridged across the said pair of conductors, and a central source of electricity having connections exterior of the said bridge for supplying the said device with energizing current, at least one of the.

said connections being through a line connection when connection is made with the line.

17. An electrical transmitting line, a connecting circuit therefor having a pair of conductors to be included in the main circuit, signal-initiating means bridged across the said pair of conductors, a central source of electricity having connections exterior of the said bridge for supplying the said signal-initiating means with electricity, and means whereby the said signal-initiating means is connected with at least one pole of the said source over a line connection when connection is made with the line.

18. The combination with a telephone line and a connecting circuit therefor having a pair of talking conductors extending from the line to the connecting circuit when the latter is connected with the line, of a permanently continuous conductive path comprising portions of the said talking conductors'and a supervisory signal-initiating device, and a central source of electricity having connections with the said talking con ductors whereby the said device is supplied with energizing current when connect-ion is made with the line, the said connections from the said source to the said talking conductors being exclusive of the said conductive path and at least one of them being made with the line portion of one of the said talking conductors.

19. The combination with a telephone line and a connecting circuit therefor having a pair of talking conductors extending from the line to the connecting circuit when the latter is connected with the line, of a permanently continuous conductive path comprising portions of the said talking conductors and a supervisory signal-initiating device, and acentral source of electricity having connections with the said talking conductors whereby the said device is supplied with energizing current when connection is made with the line, the said connections from the said source to the said talking conductors being exclusive of the said conductive path. y

20. The combination with electrical transmitting lines, of a connecting circuit there- 23. A telephone line, a connecting circuit therefor having conductors adapted to be included in the talking circuit, a signal lamp bridged across the said conductors, and a central source of electricity having connections exterior of the said bridge for supplying the said lamp with energizing current, at least one of the said connections being through a line connection when connection is made with the line.

24:. In combination, a telephone line, a connecting circuit therefor having a signalinitiating device associated therewith, a central source of electricity, means for energizing the said device from the said source while the said device is free from a shunt therearound, and means whereby the line when in use forms a shunt-circuit around the said device, relatively to the said source, to render the said device inactive.

25. In combination, an electrical transmitting line, a signal lamp, a source of electricity, means for energizing the said lamp from the said source while the said lamp free from a shunt therearound, and means whereby the line when in use forms a shuntcircuit around the said lamp to render the latter inactive.

26. The combination with an electrical transmitting line and a connecting circuit therefor, of a signalinitiating device associated with the connecting circuit, a central source of electricity, means for energizing the said device from the said source while the said device is free from a shunt therearound, and means whereby the line when in use forms a shunt-circuit around the said device, relatively to the said source, to render the said device inactive.

27. The combination with a telephone line and a connecting circuit therefor, of a signal lamp associated with the connecting cir cuit, a source of electricity, means for lighting the said lamp from the said source while the said lamp is free from a shunt therearound, and means whereby the line when in use forms a shunt-circuit around the said lamp to render same inactive.

28. The combination with a telephone line and a connecting circuit therefor, of a signal lamp constructed to carry a maximum current not greater than approxunately fiveonehundredths of an ampere and associated with the connecting circuit, a source of electricity, means for lighting the said lamp from the said source while the said lamp is free from a shunt thcrearound, and means whereby the line when in use forms a shuntcircuit around the said lamp to render same incapable of displaying a signal, the said lamp permitting a line of exceptionally high resistance to shunt it as specified.

29. The combination with a telephone line, of a signal lamp constructed to carry a maximum current not greater than ap proximately five-onelmndredths of an ampere, a source of electricity, means for lighting the said lamp from the said source while the said lamp is free from a shunt there around, and means whereby the line when in use forms a shunt-circuit around the said lamp to render same incapable of displaying a signal, the said lamp permitting a line of exceptionally high resistance to shunt it as specified.

30. The combination with a telephone line and a connecting circuit therefor, of an impedance-bridge across the main strands of the connecting circuit, a signal-initiating device, and a central source of electricity having connections exterior of the said bridge whereby a current may be sent from a line connection through the said impedance-bridge and the said signal-initiating device to effect the actuation of the latter.

31. The combination with a telephone line and a connecting circuit therefor having a pair of talking conductors extending from the line to the connecting circuit when the latter is connected with the line, of a conductive path comprising portions of the said talking conductors and a supervisory signal-initiating device, a central source of electricity having connections with the said talking conductors whereby the said device is supplied with energizing current when connection is made with the line, the said connections from the said source to the said talking conductors being exclusive of the said conductive path, and means whereby the line when in use forms a shunt-circuit around the said device to render same inactive.

32. An electrical transmitting line, a connecting circuit therefor having a conductive path comprising portions of the main strands of the connecting circuit and a signal-initiating device, a central source of electricity connected with one of the said main strands exclusive of the said path, means whereby the said signal-initiating device is connected with at least one pole of the said source over a line connection when connection is made with the line, for

energizing the said device, and means whereby the line when in use forms a shunt circuit around the said device to render same inactive.

33. An electrical transmitting line, a connecting circuit therefor having conductors for t'ansmitting the electrical transmission currcnts of the line to another line, a signal-initiating device bridged across the said conductors, a central source of electricity having connections exterior of the said bridge for supplying the said device with energizing current, at least one of the said connections being through a line connection when connection is made with the line, and means whereby the line when in use forms a shunt-circuit around the said device to render same inactive.

34. In a telephone system having lines extending from a central station to substations, a connecting circuit for the lines at the central station, a supervisory signalinitiating device bridged across the main strands of the connecting circuit, and a central source of electricity for initially energizing the said device, the said source having connections exterior of the said bridge for supplying the said energizing current.

In a telephone system having lines extending from a central station to substations, a connecting circuit forihe lines at the central. station, a supervisory signalinitiating device in a permanently continuous circuit with portions of the main strands of the connecting circuit, and a central source of electricity for initially energizing the said device, the said source having connections exterior of the said permanently continuous circuit for supplying the said energizing current.

36. In a telephone system having lines extending from a central station to substations, a connecting circuit for the lines at the central station, a supervisory signalinitiating device adapted to be bridged across the main conductors of the circuit when connection is made with a line, and a central source of electricity for initially energizing the said device, the said source having connections exterior of the said bridge for supplying the said energizing current.

37. In an electrical system having lines extending from a central station to substations, a connecting circuit for the lines at the central station, an electrically-operable device bridged across the main strands of the connecting circuit, and a central source of electricity for initially energizing the said device, the said source having connections exterior of the said bridge for supplying the said energizing current.

38. In an electrical system having lines extending from a central station to substations, a connecting circuit for the lines at the central station, an electrically-operable device in a permanently continuous circuit with portions of the main strands of the connecting circuit, and a central source of electricity for initially energizing the said device, the said source having connections exterior of the said permanently continuous circuit for supplying the said energizing current.

39. In an electrical system having lines extending from a central station to substations, a connecting circuit for the lines at the central station, an electrically-operable device adapted to be bridged across the main conductors of the circuit when connection is made with a line, and a central source-of electricity for initially energizing the said device, the said source having connections exterior of the said bridge for supplying the said energizing current.

40. In a telephone system having lines extending from a central station to substations, a connecting circuit for the lines at the central station, a supervisory signalinitiating device bridged across the main strands of the connecting circuit, and a central source of electricty for initially energizing the said device, the said source having connections exterior of the said bridge for supplying the said energizing current, the said device being shunted by a line circuit and thereby rendered inactive when connection is made with a line in use.

41. In a telephone system having lines ex tending from a central station to substations, a connecting circuit for the lines at the central station, a supervisory signal-initiating device in a permanently continuous circuit with portions of the main strands of the con necting circuit, and a central source of electricity for initially energizing the said device, the said source having connections exterior of the said permanently continuous circuit for supplying the said energizing current, the said device being shunted by a line circuit and thereby rendered inactive when connection is made with a line in use.

42. In a telephone system having lines extending from a central station to substations, a connecting circuit for the lines at the central station, a supervisory signalinitiating device adapted to be bridged across the main conductors of the circuit when connection is made with a line, and a central source of electricity for initially energizing the said device, the said source having connections exterlor of the said bridge for supplying the said energizing current, the said device being shunted by a line circuit and thereby rendered inactive when connection is made with a line in use.

43. In an electrical system having lines extending from a central station to substations, a connecting circuit for the lines at the central station, an electrically-operable device bridged across the main strands of the connecting circuit, and acentral source of electricity for initially energizing the said device, the said source having connections exterior of the said bridge for supplying the said energizing current, the said device being shunted by a line circuit and thereby rendered inactive when connection is made with a line in use.

44. In an electrical system having lines extending from a central station to substations, a connecting circuit for the lines at the central station, an electrically-operable device in a permanently continuous circuit with portions of the main strands of the connecting circuit, and a central source of electricity for initially energizing the said device, the said source having connections exterior of the said permanently continuous circuit for supplying the said energizing current, the said device being shunted by a line circuit and thereby rendered inactive when connection is made with a line in use.

45. In an electrical system having lines extending from a central station to substa tions, a connecting circuit for the lines at the central station, an electrically-operable device adapted to be bridged across the main conductors of the circuit when connection is made with a line, and a central source of electricity for initially energizing the said device, the said source having connections exterior of the said bridge for supplying the said energizing current, the said device being shunted by a line circuit and thereby rendered inactive when connection is made with a line in use.

46. The combination with electrical transmitting lines, of a connecting circuit therefor containing a signal-initiating device, a source of electricity, means for energizing the said device from the said source while the said device is free from a shunt therearound, and means whereby the circuit of a line forms a shunt around the said device to render same inactive, when connection is made with the line.

47. The combination with a telephone line, of a signal lamp constructed to carry a maximum current not greater than approximately five-onehundredths of an ampere, a source of'electricity for supplying current to light the said lamp, and means whereby the line when in use forms a shunt around the said lamp to render same incapable of displaying a signal, the said lamp permitting a line of either low or exceptionally high resistance to shunt it as specified' 48. The combination with a telephone line and a connecting circuit therefor, of an impedance-bridgeacross the main strands of the connecting circuit, a signal-initiating subscribe my name in the presence of two device, and a central source of electricity havsubscribing witnesses, this 1st day of August,

ing connections exterior of the said bridge whereby a current may be sent through the A. D., 1904. said impedance-bridge and the said signal- FREDERICK R. PARKER. initiating device to effect the actuation of Witnesses:

R. G. PARKER,

the latter.

WM. F. VIOLETT.

As inventor of the foregoing, I hereunto Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. O. 

